Abstract: This invention provides a temperature-compensated piezoelectric oscillator having an oscillation frequency that is easily adjusted in an adjustment procedure after its assembly. Compensation for frequency-temperature characteristics is achieved without the need for an externally installed variable reactance element. The temperature-compensated piezoelectric oscillator includes a piezoelectric oscillator element and an oscillator circuit that drives the piezoelectric oscillator element. The oscillator circuit changes the oscillation frequency in response to an applied power supply voltage VDD(T). A temperature sensor circuit senses the ambient temperature T of the piezoelectric oscillator element. A variable power supply circuit changes the power supply voltage VDD(T) applied to the oscillator circuit in response to the temperature sensed by the temperature sensor circuit. The changes in the applied power supply voltage VDD(T) changes the frequency-temperature characteristics of the oscillator circuit.